Officially deprecate "django"

See https://github.com/docker-library/docs/pull/503 for the justification of the deprecation of `rails`, which all applies here as well.

django/deprecated.md

@@ -0,0 +1,22 @@
+This image is officially deprecated in favor of [the standard `python` image](https://hub.docker.com/_/python/), and will receive no further updates after 2016-12-31 (Dec 31, 2016). Please adjust your usage accordingly.
+
+For most usages of this image, it was already not bringing in `django` from this image, but actually from your project's `requirements.txt`, so the only "value" being added here was the pre-installing of `mysql-client`, `postgresql-client`, and `sqlite3` for various uses of the `django` framework.
+
+For example, a `Dockerfile` similar to the following would be a good starting point for a Django project using PostgreSQL:
+
+```dockerfile
+FROM python:3.4
+
+RUN apt-get update \
+	&& apt-get install -y --no-install-recommends \
+		postgresql-client \
+	&& rm -rf /var/lib/apt/lists/*
+
+WORKDIR /usr/src/app
+COPY requirements.txt ./
+RUN pip install -r requirements.txt
+COPY . .
+
+EXPOSE 8000
+CMD ["python", "manage.py", "runserver", "0.0.0.0:8000"]
+```